Two principle types of semi-trailer sidewall constructions are commonly employed in this field of art. The frequently used "post and sheet panel" construction method typically involves the installation of spaced metallic vertical posts upon a semi-trailer and the subsequent attachment to these posts of sheet panels having various compositions. These vertical posts inevitably detract from the available volume within the semi-trailer either by protruding into the cargo area themselves or by affixing the sidewall in a position which is inward from the maximum width of the trailer. These vertical posts limit the useful cargo volume inside the trailer because the overall width of trailers is constrained by regulation. Moreover, such post and sheet panel trailers are comparatively heavy. Trailer constructions which fall into this type of category are disclosed in U.S. Pat. Nos. 3,216,758 and 4,042,275.
Some of the disadvantages relating to internal usable volume have been addressed more recently in the second principle type of trailer sidewall construction referred to as "plate" trailers. Plate trailers employ thin aluminum plates or composite materials joined by relatively flat rectilinear strips which secure the plates in a side-by-side relationship. These types of sidewalls have been employed in semi-trailers in order to maximize the width, and cubic capacity, of the cargo carrier. However, while some of these designs succeed in optimizing the internal volume of the cargo carrier, they also necessarily sacrifice columnar strength of the trailer sidewalls.
Moreover, the joining mechanism employed in typical plate-type trailer applications requires a large number of fasteners, such as rivets, to accomplish the joining of the plates which comprise the trailer sidewalls. Inherent in such throughbore fastening systems is the potential for water leakage. Many of these designs are subject to even further water leakage through voids in the seams created by imperfections in plate edges. Indeed, extreme care must be exercised in the handling of these plates in order to insure a clean and smooth seal. Those designs which address leakage by employing flexible seals within joining members nonetheless require a large number of mechanical fasteners. Such a process substantially adds to the production costs associated with the design.
Other special problems noted in plate trailers employing thin, flat sidewalls are a susceptibility to sidewall punctures and inferior columnar strength. As a result of inferior columnar strength, joining members must be spaced more closely together in higher weight and stress-bearing regions of the carrier sidewall. Such a design only creates the need for more seams which are susceptible to leakage and which complicate the production process by, among other things, creating the need for a plurality of plate sizes. Trailers which fall into the above-described category are disclosed in U.S. Pat. Nos. 4,810,027; 5,058,756; 5,066,066; and 5,112,099.